This invention relates to vibrating mass gyroscopes and to how force-applying signals and sensed output signals are implemented.
An axisymmetric vibrating gyroscope can be considered to be a classic two dimensional oscillator. A pictorial representation of a dynamic model of such a gyroscope is shown in FIG. 1. In operation the mass M is dithered along one axis, e.g. the x-axis, wherein the mass M is driven so that it vibrates along the x-axis. The output of the other axis, the y-axis in this example, senses the Coriolis forces generated by the angular rate Ω. The Coriolis forces act in a direction at right angles to the direction of vibration and to the axis of the rotation. The amplitude of any vibration along the sense axis is driven to zero by a feedback loop, e.g. a servo loop. The modes are then reversed, i.e. the x-axis becomes the sensing axis and the y-axis becomes the axis along which the mass is driven, in an attempt to cancel common error terms. As will be explained in greater detail below, bias error cancelation may require more than just mode reversal only. Therefore, a need exists to minimize bias errors in a vibrating mass gyroscope using techniques such as described below.